<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>计时器</title>
  <script>
    var hour,minute,second;//时 分 秒
    hour=minute=second=0;//初始化
    
    var int;
    var millisecond=0;//毫秒
    function Reset()//重置
    {
      window.clearInterval(int);
      millisecond=hour=minute=second=0;
      document.getElementById('timetext').value= '00时00分00秒' ;
    }
    function start()//开始
    {
      int=setInterval(timer,1000);
    }
    //计时
    function timer(){
        second++;
      if(second>=60){
        second=0;
        minute=minute+1;
      }
      if(minute>=60){
        minute=0;
        hour=hour+1;
      }
      document.getElementById('timetext').value=hour+'时'+minute+'分'+second+'秒';
    }
  </script>
</head>
<body>
<div style="text-align: center">
  <input type="text" id="timetext" value="00时00分00秒" readonly><br>
  <button type="button" onclick="start()">开始</button> <button type="button" onclick="stop()">暂停</button> <button type="button" onclick="Reset()">重置</button>
</div>
</body>
</html>